1. Field of the Invention
This invention relates to an ink-jet recording ink, and an ink-jet recording process and an ink-jet recording apparatus which make use of the same. More particularly, this invention relates to an ink-jet recording ink (hereinafter simply “ink”) which is suited for an ink-jet recording process, may cause no problem of curling of recording mediums even when a water base ink is applied in a large quantity to a cellulose-containing recording medium, and also can give a good response at the time of high drive frequency ink ejection and good sticking resistance to recording head.
2. Related Background Art
The ink-jet recording process is a process in which minute droplets of an ink are caused to fly and adhere to a recording medium such as paper to perform recording. An ejection system in which, using an electricity-heat converter as a means for feeding ejection energy, heat energy is imparted to the ink to produce air bubbles to eject the droplets is called a thermal system. According to this system, the recording head can easily be made multiple-nozzle in a high density, and images with a high resolution and a high quality can be recorded at a high speed (see, e.g., Japanese Patent Publications No. S61-59911, No. S61-59912 and No. S61-59914).
In recent years, in order to make adaptation to very high grade ink-jet recorded images at a level of silver salt photography, the droplets of ink ejected from a single nozzle have become small in size. At present, ink-jet printers of about 5 pl (picoliters) or less in ink droplet quantity are on the market. In regard to recording speed as well, printers are being demanded to be made much more high-speed. With such a demand, in regard to the ink, it is a matter of urgency to make adaptation to a higher drive frequency and to achieve an improvement in what is called sticking resistance, in virtue of which the sticking of ink can effectively be kept from occurring around the recording head.
As inks used in ink-jet recording, what are commonly available are those composed chiefly of water which is a medium for dissolving or dispersing a coloring material therein, and containing a water-soluble high-boiling solvent such as glycol added for the purposes of, e.g., preventing ink from drying and improving the sticking resistance to recording head. Then, in instances in which recording is performed using such inks on cellulose-containing recording mediums such as plain paper, light weight coated paper, and base paper absorption type coated paper, what is called the curling may occur in which the recording medium comes to warp when the ink is applied thereinto in a large quantity in a short time at its regions having a certain or larger area. The occurrence of such curling has not so much come into question in the recording of character and letter base images that has hitherto been prevalent, because the recording is performed in a small ink application amount. However, when internet home pages are recorded or photographic images are recorded as having come to be widely done in recent years, inks must be applied in a large quantity into plain paper or the like, and hence the occurrence of curling is one of large problems to be resolved.
To cope with such a problem, a water base ink composition is proposed which contains a curl preventive material of various types (see, e.g., Japanese Patent Application Laid-open Nos. H06-157955 and 11-12520). In inks making use of such a material, an effect is seen to a certain extent in respect of curling resistance (which means that the effect of keeping curl from occurring is seen). However, further improvement is desired in respect of achievement of both the response at the time of high drive frequency ink ejection or the sticking resistance and the curling resistance.
Meanwhile, a proposal is made on an ink containing a block compound (which has a small molecular weight for it to be called a block copolymer, and hence is called a block compound in the present invention) having an ethylene oxide moiety and a propylene oxide moiety in its structure (see, e.g.,Japanese Patent Publication No. H03-43313 and Japanese Patent No. 2894202). However, in the ink disclosed in these publications, it has been desired to overcome at a higher level the technical subject of how to achieve both the response at the time of high drive frequency ink ejection or the sticking resistance and the curling resistance.